Study of the effects of Casein Kinase II Phosphorylation of the N-terminal extension of bHLHz Max. Using the proteolysis-mass spectrometric assay developed to study bHLHz Max. It was shown that phosphorylated Max binds to Max-specific DNA at room temperatures, contradicting earlier studies that used electrophoretic mobility shift assays. Effects of phosphorylation on the structure of the protein was also studied by circular dichroism and ultracentrifugation assays.